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WAEC Mathematics 2015 Paper

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Question : 25

Total: 45

Scores	$0-4$	$5-9$	$10-14$
Frequency	2	1	2

The table shows the distribution of the scores of some students in a test. Calculate the mean scores.

5.6
6.2
6.6
7.0

Solution:

Concept:

Mean of grouped data is found using class midpoints and their frequencies.

Explanation:

Find the midpoint of each score interval.

0-4

midpoint is

\frac{0+4}{2} = 2

5-9

midpoint is

\frac{5+9}{2} = 7

10-14

midpoint is

\frac{10+14}{2} = 12

Multiply each midpoint by its frequency.

2 \times 2 = 4

1 \times 7 = 7

2 \times 12 = 24

Add the products:

4 + 7 + 24 = 35

Add the frequencies:

2 + 1 + 2 = 5

Mean

= \frac{35}{5} = 7

Answer:

D.

7.0

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